Bearings are used to reduce frictional forces between two or more parts that are configured and designed to have relative motion and provide support therebetween. In general, bearings can be classified as sliding bearings in which the bearing elements are separated by a film of lubricant and rolling element bearings in which ball bearings, roller bearings, needle bearings, and the like are provided between the moving parts.
Slide-type bearings include all varieties of bearings in which the primary motion involves sliding one surface over or against another. Accordingly, all types of journal or sleeve bearings which are used to position a shaft or movable part in a radial direction are slide-type bearings. Moreover, all types of thrust bearings, which are used in general to prevent movement of a rotating shaft in an axial direction and as guides for linear motion of various types are also slide-type bearings.
Conventional bearings require a lubricant such as a grease or oil that is often periodically applied between the bearing surfaces, i.e., the surfaces of the bearing elements and any surface that are opposed and moved relative to the bearing elements.
A significant improvement over conventional bearings was the development of self-lubricating bearings which incorporate lubricant materials or compositions into the bearing design so that a layer of lubricant is provided and maintained between the bearing surfaces.
Self-lubricating bearings are particularly useful in extreme environments where temperature extremes can degrade conventional lubricants or adversely affect their performance. Self-lubricating bearings also can be used in applications in which conventional lubricants may present an undesirable contamination such as for example in food, textile, drug, pollution control, printing applications, etc. In other applications in which conventional lubricants can adversely react chemically, such as in chemical processing and plating equipment, self-lubricating bearings idea.
A common self-lubricating bearing design includes a bearing structure that is provided with pockets or cavities in the bearing surface into which a lubricating component such as graphite is held. In use, a thin layer of the lubricating component is distributed from the pockets or cavities between the bearing surfaces.
Conventional materials from which self-lubricating bearings are made include copper alloys such as bronze, aluminum bronze, manganese bronze and hardened steel and steel-backed copper alloy structures.
Conventional solid lubricants that are used in self-lubricating bearings include amorphous graphite, polyimide graphite fiber reinforced composites, and molybdenum disulfide.
The present invention is directed to self-lubricating bushings, bearings and bearing assemblies that include unique configurations of solid lubricant inserts.